This invention relates to a writing screen which is a film having an advantage in that it may be formed easily and comprising a specific vinylidene fluoride copolymer resin and has excellent marker suitability (ink affinity and erasability for ink) and resistance to surface damage.
Recently, there have been marketed writing boards (white boards) on which writing is carried out with a marker. There have also been developed articles which are, for example, in combination with an electronic duplicating function and are distinguished from conventional black boards on which writing is conducted with chalks. These white boards are now expected to undergo still more development with improvement and modification.
The surface overlaying films of these white boards are required to have marker suitability, that is, a property whereby ink spreads homogeneously without blotting or repelling of ink (ink drapeability) and ink writing can be easily and completely erased with an eraser (ink erasability). Therefore ethylene-tetrafluoroethylene copolymers have conventionally been used.
However, an ethylene-tetrafluoroethylene copolymer has a narrow temperature range in which it can be molded because of its high melting temperature and needs a special molding process for use, which makes its handling complicated and thus uneconomical. Moreover, it tends to be scratched and otherwise damaged because of its softness.
An object of this invention is to provide a screen which can be formed with a film obtained by a simple molding process and is economical.
Another object of this invention is to provide a screen which is damage resistant and has excellent marker suitability.
We have conducted a variety of researches with respect to resins which have low melting points and can easily be molded for the purpose of improving the aforementioned points.
However, sufficient marker suitability was not obtained by simply applying a low melting resin. No improvement was observed even in a blend of a high melting resin and a low melting resin.